1. Field of Invention
The present invention relates to a prostheses device, system and method for replacing a portion of bone forming a part of a joint, and more particularly to a prosthesis device that is positionable, in situ, in the correct anatomical alignment with the joint and to a system and method for aligning the prosthesis, intraoperatively.
2. Description of the Related Art
Prostheses systems for replacing part of a joint are known in the art. For example, in connection with the elbow joint, modular prostheses systems for replacing the head of the radius exist that provide for replicating the different diameters of a resected radial head, as well as, for allowing adjustability of the overall length of the prostheses. These known devices permit a surgeon to install a radial head prosthesis that generally approximates the original geometrical relationship between the radial head, the capitellum of the humerus and the radial notch of the ulna.
For example, U.S. Pat. No. 6,270,529 (the “'529 patent”) to Terrill-Grisoni discloses a modular implant and system for replacing the radial head. The system of the '529 patent includes modular radial head implants, sizers for trial reduction of the joint, and instrumentation for preparing the radial head, trialing the sizers, and assembling the implants. Similarly, U.S. Pat. No. 6,656,225 (the “'225 patent”) to Martin discloses a modular radial head prostheses and system including a stem component having an anchoring portion and a mounting portion, and a head component having an open channel wherein the open channel is configured to connect to the mounting portion along an assembly axis that is transverse to a longitudinal axis of the stem component. Although such modular, adjustable prostheses provide for some degrees of adjustability of the position of the radial head prosthesis to the capitellum of the humerus, the ability to provide even further degrees of adjustability would be advantageous. In particular, since these devices do not explicitly address the angular alignment of the prosthesis to the capitellum in the relevant planes it has been observed that, after implantation, they can “wobble” in the joint in a way similar to the wobble of the wheel of a vehicle that is not correctly aligned to its axle.
In an attempt to address the alignment issue other types of radial head prostheses have been devised wherein the prosthetic radial head is allowed to swivel freely, within a certain range, relative to the medullary canal of the radius bone. For example, U.S. Pat. No. 5,879,395 to Tornier et al., (the “'395 patent”), discloses an elbow prosthesis including a radial element having an anchoring stem provided with a neck which is inclined by an angle of between 0 and 30 degrees relative to the axis of the anchoring stem. In the '395 patent, the neck is integral with a ball on which a cylindrical head articulates. Such devices are known in the art as “bipolar” prostheses. Other bipolar prostheses are disclosed in United States Patent Application Publication No. 2006/0142866 to Baratz and in PCT Application Publication No. WO07/109,752 to Vander Meulen. Additionally, a bipolar prosthesis, in the context of a radial-capitellar implant, is disclosed in U.S. Pat. No. 7,160,329 to Cooney.
While these types of prostheses intend to reduce or eliminate the wobble, it has been noted that, rather than provide the correct alignment of the radial head prosthesis to the capitellum, bipolar prostheses allow for multiple alignments of the head that constantly change as the joint traverses through its natural range of motion and are prone to lock themselves into an extreme alignment, leading to subluxation and/or continued instability of the joint.
What is needed is a device, system and method that overcomes the disadvantages of known prostheses. In particular, there is needed a device, system and method for replacing a portion of a bone making up a joint, wherein the natural axis of rotation of the joint can be identified intraoperatively, and wherein the prosthesis can be fixed in the identified anatomical alignment of the joint.